We’re now one hypothesis down and know one thing more: tens of millions of years ago there was an enormous piece of floating rock that did not cause the dinosaurs to die out at the Cretaceous-Tertiary boundary, NASA scientists say.
This however does not mean that the famous mass extinction event before the onset of the Tertiary – during which the Earth’s fossil record had to say goodbye to all dinosaurs but the birds, and which marks the sudden end of those abundant and cheerful ammonites in marine rocks – was not caused by any asteroid.
Baptistina crashed in asteroid belt
It just wasn’t caused by debris of Baptistina, a large asteroid which we thought had entered our solar system almost a hundred million years before the C-T boundary [which itself dates back 66 million years], crashing into other orbiting bodies in the so-called asteroid belt between Jupiter and Mars.
Based on infrared measurements of remaining Baptistina debris in the asteroid belt by NASA’s WISE project, scientists were better able to determine the size of the original asteroid, which turns out to have been much smaller. This also influences chronology. The asteroid is now thought to have entered our solar system 80 million years ago, just half the previous time estimate.
In the remaining 15 million years before the end of the Cretaceous period and the end of the dinosaurs it is now thought unlikely it was capable to send a chunk to Earth, big enough to have caused the extinction. That’s because it would take many millions of years to reach sufficient deviation from its orbit.
Found a likely jar, looking for a fitting lid
The WISE project is now looking to disentangle other asteroid families, size them up, and date them. They hope to find one that matches the famous crater deep under the Gulf of Mexico.
The C-T extinction event is actually quite odd in Earth’s history of extinction events in that is (still) thought to have been caused by an extraterrestrial influence. Usually some big tug in the climate system was sufficient to do the trick – even for the one that dwarfed all others to the size of a flu epidemic.
© Rolf Schuttenhelm | www.bitsofscience.org